Thermocompression techniques have been employed in the past for effecting a seal between a metallic container and an .alpha.-alumina ring for sodium-sulphur high temperature cell as exemplified by U.S. Pat. No. 4,037,027 to Desplanches et al. However, the technique and materials disclosed are not effective for lithium-based cells. The peripheral seals create a container or envelope for the cell electrochemistry and permits bipolar stacks of plural cells to be effected in a one-shot operation. Such peripheral seals must be a good electrical insulator at cell operating temperatures on the order of 400.degree. to 500.degree. C., the peripheral seal structure must be chemically stable at such high temperature, must involve a match of thermal expansion coefficients for the components of the cells, provide a strong mechanical bond to metals and/or ceramics and provide an effective barrier to molten salt.
U.S. Pat. No. 5,279,909 to Horner et al. is directed to a compact bipolar battery cell which includes extremely thin metal-ceramic metal seals which is used to electrically insulate the battery's anode current collector from its cathode current collector with the seals preventing leakage of the battery's electrolyte from between the anode and cathode, and wherein the seals are made from layers of powder which are sintered together in a monolithic structure.
U.S. Pat. No. 5,162,172 to Kaun is directed to the production of bipolar batteries of a plurality of cells which are sealed at their peripheries and which employ cup-like electrode holders open at the top to receive individual elements such as the negative and positive electrodes, the separator element, etc., and which includes perimeter metallic seal rings and ceramic seal rings to complete an electrode containment structure.
Such bipolar batteries as exemplified by Horner et al. and Kaun are either complicated in structure and require individual peripheral seals as each level of the stacked array is completed utilizing the cup-shaped holders in order from the bottom of the stack to the top as in Kaun, or simultaneous sintering of a multi-layer stacked structure of compressed ceramic and metallic powders, thereby requiring close control of the material content of the ceramic/metallic constituents of the sintered multi-layer structure.
It is therefore a primary object of this invention to provide a compact, hermetically peripherally sealed bipolar multi-cell alloy/FeS.sub.x battery which utilizes specially formed and configured spacer rings in conjunction with like thermal coefficient of expansion current collector cups, allowing easier and more economically constructed peripherally sealed modular units, eliminating the need for electrode locators, and permitting steel-to-steel welding to hermetically close the cell envelope of at least two seal assemblies, and where peripheral sealing between juxtaposed components is effected by thermocompression and diffusion bonds.